Cultivation in long-term simulated microgravity is detrimental to pyocyanin production and subsequent biofilm formation ability of .

UNLABELLED

forms aggregates known as biofilms. Previous studies have shown that when is cultivated in space, thicker and structurally different biofilms are formed than from those grown on Earth. We investigated how microgravity, simulated in a laboratory setting, influenced the growth, colonization, and virulence potentials of a PA14 wild-type strain, as well as two surface attachment-defective () mutants altered at crucial biofilm-forming steps: and . Using high-aspect ratio rotating-wall vessel (HARV) bioreactors, bacteria were grown to stationary phase under prolonged (6 days) exposure to simulated microgravity or normal gravity conditions. After the exposure, the capacity of the culture to form biofilms was measured. Additionally, pigment (pyocyanin) formed by each culture during the incubation was extracted and quantified. We demonstrate that the first prolonged exposure to low-shear modeled microgravity (LSMMG) and without nutrient replenishment significantly diminishes wild-type PA14 biofilm formation abilities after exposure and pyocyanin production during exposure, while the mutant strains exhibit differing outcomes for both properties.

IMPORTANCE

Given plans for humans to engage in prolonged space travel, we investigated biofilm and pigment/virulence factor formation in when cultivated in microgravity. These bacteria are opportunistic pathogens in immunocompromised individuals. Previous studies of space travelers have shown some immune system diminutions. Hence, our studies shed some light on how prolonged cultivation of bacteria in simulated microgravity conditions affect their growth characteristics.